1. Department of Applied Mathematics, School of Mathematics and Statistics, Beijing Key Laboratory on MCAACI Beijing Institute of Technology Beijing People's Republic of China
2. Department of Mathematics Northwest Normal University Lanzhou Gansu People's Republic of China
3. Department of Mathematics, European Centre of Excellence NTIS—New Technologies for the Information Society University of West Bohemia Pilsen Czech Republic
4. Department of Mathematics Henan University Kaifeng People's Republic of China